Separation of olefinic fatty acids



United States Patent Edwin Marshall Meade, Richmond Hill, Ontario, Canada No Drawing. Application September 25, 1956 Serial No. 612,059

Claims priority, application Great Britain October 1, 1955 16 Claims. (Cl. 260-419) This invention relates, as indicated, to the separation of olefinic fatty acid compounds and more particularly to the preparation of concentrates of the mono-olefinic and poly-olefinic fatty acid compounds derived from natural fatty materials.

Tall oil is a by-product of the kraft or sulphate paper process. In this process, wood chips are cooked with sodium sulfate liquor which dissolves the lignin and saponifies all fatty materials. At the end of this process the cellulose is separated from the so-called black liquor, which contains all these products in solution. The black liquor is concentrated until the strength is reached at which the soaps become insoluble and rise to the surface. They are collected and are called at this stage black liquor skimmings. These skimmings are then acidulated and a mixture of free fatty acids and free resin acids is formed which is the crude tall oil of commerce. This crude tall oil is normally distilled once in order to free it from the gross impurities and the distillate is carefully vacuum fractionated. By this process the fatty acids are freed from practically all the resin acids and from most of the unsaponifiable matter, and various grades of tall oil fatty acids are on the market with resin contents varying from 30% down to as low as 1% or even less, containing oleic and linoleic acids.

It will be readily apparent that if oleic and linoleic acids can be separated, it would provide an additional means for utilizing the fatty acids derived from tall oil. Similarly, commercial red oil, cottonseed oil fatty acids, and soyabean oil fatty acids contain mixtures of monoand poly-olefinic acids. These also would have additional outlets in commerce if they could be divided into their respective components.

It is, therefore, an object of the invention to provide a. process for the separation of olefinic fatty acid compounds, particularly those mixtures derived from natural fatty materials.

Itis a still further object of the invention to provide a method for obtaining fractions of oleic and linoleic acid compounds from mixtures thereof.

It is yeta further object of the invention to provide a process for separation into concentrates of olefinic fatty acid compoundswhich is operable on very crude undistilled acids and their correspondingly impure soaps.

It is another object of the invention to provide a process for-separating mixtures of olefinic fatty acid compounds, which is inexpensive and suitable for commercial operations by reason of the savings of solvents, refrigeration and plant unit capacity.

To the accomplishment of the foregoing and related ends, saidinvention then comprises the features hereinafter fullydescribed and particularly pointed out in the claims, the following description setting forth in detail cfllftain illustrative embodiments of the invention, these being indicative, however, of but a few of the various wa s, which the principle of the invention may be m la e In "accordance with the objects of the invention, it has oleate, a new and hitherto undescribed substance, is a whlte powder which gels in water, dissolves readily in- 2,915,537 Patented Dec. 1, 1959 Broadly stated, the present invention relates to a proc-.

ess for separating a mixture containing mono-olefinic and poly-olefinic fatty acid compounds which comprises the steps of: forming acid-soaps of the mono-olefinic fatty acid compounds of said mixture in situ, maintaining said mixture at a temperature within the range from about 55 C. to about 25 C. in the presence of a low molecular weight organic solvent whereby said acid-soaps of the mono-olefinic fatty acids precipitate as a solid phase, and then separating the solid from the liquid phase. In its broadest aspects the invention also is concerned with the sodium and ammonium acid-soaps of olefinic fatty acids as new compounds.

The starting material mixtures suitable for the process are in general mixtures containing monoand poly-olefinic fatty acids and/or the soaps thereof, such as those obtained from natural fatty materials, in which the monoolefinic acid compounds are present in amounts of at least 2 percent by weight; but the process is more economically suited to mixtures containing 5% to 95% by weight of mono-olefinic fatty acid compounds. These olefinic fatty acids are mono-carboxylic and generally. contain from sixteen to twenty-two carbon atoms. Ex-

amples of typical mixtures that may be employed in the process of the invention include the fatty acid compounds. obtained from tall oil fatty acids, cottonseed oil fatty acids, soyabean oil fatty acids, commercial red oil or oleine, and the like. The process is especially useful inv separating oleic from linoleic acids in mixtures thereof.

Formation of the aicd-s'oap of the mono-olefinic fatty acid in the mixture may be accomplished by partial neu-' tralization of the mixture employing a base which has monobasic inorganic ionswhich form water soluble normal soaps. The partial neutralization is generally with in the range of about 40% molecular of the monoole finic fatty acids and not more than molecular of the total fatty acids. Suitable'bases include sodium hydrox A ide, potassium hydroxide, and ammonium hydroxide. Also partial neutralization may be accomplished by adding a soap of a fatty acid to the fatty acid mixture. Alternatively the mixture of fatty acids may be completely neutralized to their normal soaps which are then acidified by addition of a fatty acid or by treatment with a mineral acid to cause the formation of the acid soaps of monoolefinic fatty acids.

t The acid-soaps which precipitate in the process are of f the approximate formula MX-HX, wherein X is the radical of a mono-olefinic fatty acid having from sixteen" to twenty-two carbon atoms; M is sodium, potassium, or ammonium, and H is hydrogen. Sodium hydrogen diwarm alcohols or hot acetone, melts over a wide range of about 30-100 C., and gives a purified oleic acid almost free from linoleic acid on acidulation. Ammonium hydrogen dioleate, also a new and hitherto undescribed substance, is a white crystalline powder which readily loses ammonia in the air, especially on warming.

It dissolves much more readily than sodium hydrogendi-oleate, and requires lower temperatures for its crystallization.

The mixture containing the acid-soap of the mono olefinic fatty acid is cooled ordinarily to a temperature within the range from about 55 C. to about 25 C. in the presence of a low molecular weight organic solvent. Although this temperature range embraces various combinations of materials, it will be realized that the range varies somewhat for particular acid-soaps and solvents. For example, the temperature range for the sodium and potassium acid-soaps in an acetone solvent will be from about 25 C. to about 25 C.; sodium and potassium acid-soaps in methyl alcohol will be from about 45 C. to about C.; and ammonium acidsoaps in acetone will be from about 55 C. to about 20 C.

The organic solvents employed are low molecular weight compounds. Suitable solvents are the alcohols and ketones containing not more than four carbon atoms. Examples of these include methanol, acetone, ethanol, propanol, isopropanol, and methyl ethyl ketone. The water content of the solvent should not be more than by weight to avoid separation into two liquid layers, or an ice phase on cooling. The amount of solvent is broadly from about two to ten, preferably three to five, parts by weight of the solvent to one part of the fatty acid mixture.

In order to more clearly illustrate our invention and the preferred modes of carrying the same into efiect, the following examples are given, in which the term parts, whenever it is used, means parts by weight:

Example 1.-280 parts of the mixture of fatty acids obtained by the close vacuum fractionation of tall oil, containing less than 2% of resin acids, and comprising about equal parts of oleic and linoleic acids were added to 840 parts of 95% acetone, and then 12 parts of sodium hydroxide dissolved in 42 parts of water were added with vigorous agitation, and the mixture cooled to C. with slow agitation. The mixture was then filtered under vacuum, and the solid phase of acid soaps washed with 90% acetone which had been precooled to -20 C., until the washings were colorless. The solid and liquid phases were separately acidulated with dilute sulphuric acid so as to decompose soaps and liberate the fatty acids, and then acetone was recovered by distillation, and the fatty acids washed free of inorganic salts by water. The solid phase yielded about 150 parts of a com centrate of the mono-olefinic acids, and had an iodine value of 99.5: the filtrates yielded about 130 parts of a concentrate of the poly-olefinic acids, and had an iodine value of 169.0.

Example 2.--280 parts of cottonseed oil fatty acids were added to 1120 parts of 95 methanol containing 16 parts of sodium hydroxide, and the solution obtained was cooled to C., filtered under vacuum, and washed with 95% methanol precooled to 30. The solid and liquid fractions were then worked up as described in Example 1, the solid phase of acid soaps giving about 140 parts of a mixture of I.V. 52.0, comprising the saturated acids together with a concentrate of the mono-olefinic acids relatively free from poly-olefinic acids, and the filtrate gave about 140 parts of a concenirate of the poly-olefinic acids of I.V. 148.

Example 3.280 parts of soyabean oil fatty acids were dissolved in 1120 parts of methyl ethyl ketone, and 14 parts of potassium hydroxide in 45 parts of water added, and the mixture cooled to C. and filtered. The filtrate was heated to 100 C., finally under vacuum, and was then washed with dilute sulphuric acid, giving a concentrate of the poly-olefinic acids of I.V. 158.

.Example 4.280 parts of the tall oil fatty acids used in Example 1 were dissolved in 840 parts of 99.5% methanol, and a solution of 8.5 parts of ammonia in 100 parts of methanol added beneath its surface with agitation. The solution obtained was cooled to around C., and filtered from a solid phase of acid soaps which contained a concentrate of the mono-olefinie acids. The filtrate was dropped in a thin stream into a vessel maintained at 130 0., thereby causing the methanol to flash ofi together with the ammonia liberated by the thermal dissociation of the ammonium acid soaps leaving a concentrate of the poly-unsaturated acids, which had an iodine value of 167.

Example 5.280 parts of a commercial red oil, that is, crude oleic acid from animal oil, which had a titre of about 0 C. and an iodine value of 98.5, and con tained about 15% of linoleic acid, were dissolved in 1120 parts of 90% methanol, and cooled to 0 C., only traces of solids separating. parts of 40% caustic soda full solution.

liquor dissolved in 560 parts of methanol were separately cooled to -15 C., and were then added to the acid solution with good agitation, causing a rapid precipitation of sodium hydrogen dioleate as a white powder. After standing overnight at 15'C., the product was vacuum filtered and washed with methanol precooled to 15 C. until the washings were colorless. The solid and liquid phases were worked up as in Example 1, the solid yielding about 200 parts of an oleic acid concentrate of I.V. 84.6 which contained palmitic acid but little linoleic acid, and the liquid yielding about parts of a concentrate of the linoleic acid of I.V. 129.

Example 6.-280 parts of commercial red oil (oleine) from beef tallow were dissolved in 1120 parts of methanol, cooled to 10 C., and filtered from about 12 parts of saturated acids. 26 parts of warm 70% caustic soda liquor dissolved in 100 parts of methanol were added with intense stirring, and the solution .allowed to crystallize at 20 C., filtered and washed 'with precooled methanol. The solid, which was mainly sodium hydrogen dioleate, was then dissolved in 500 parts of dry methanol and recrystallized at 0 C.; the solid was further recrystallized first rejecting a crop at 10 C. which contained mixed sodium hydrogen oleate palmitates, and then taking an almost pure crop of dioleate at 0 C. Sodium hydrogen dioleate, a new and hitherto undescribed substance, is a white powder which gels in water, dissolves readily in warm alcohols or hot acetone, melts over a wide range of about 30-l00 C., and gives a purified oleic acid almost free from linoleic acid on acidulation.

Example 7.-The once purified oleic acid obtained in Example 5 was dissolved in 5 parts of acetone, cooled to 20 C., and filtered from a precipitate of saturated acids. 0.03 part of ammonia, freshly dissolved in 0.5 part of cold acetone, was then added, and the solution cooled to 45 C. to precipitate ammonium hydrogen dioleate. This was filtered off and recrystallized from 5 parts of acetone at 20 C. Ammonium hydrogen dioleate, also a new and hitherto undescribed substance, is a white crystalline powder which readily loses ammonia in the air, especially on warming. It dissolves much more readily than sodium hydrogen dioleate, and requires lower temperatures for its crystallization.

Example 8.-280 parts of distilled soya bean oil fatty acids of I.V. 127.5 were dissolved in 900 parts of acetone, and 10 parts of sodium hydroxide dissolved in 50 parts of water added slowly with good agitation and cooling, finally to 10 C. The solid was then filtered and washed with acetone precooled to 0 C., leaving solid acid soaps which contained a concentrate of the monoethylenic acids together with the saturated acids of I.V. 43, the combined filtrates containing a concentrate of the linoleic and linolenic acids of I.V. 147.

Example 9.Alkali refined cottonseed oil soapstock was acidulated, and the split fatty acids dissolved in three parts of 98% acetone, and then brought to about 30% neutralization by adding the requisite amount of the unsplit highly alkaline soapstock, warming to obtain This solution was stood at an ambient temperature of 20-25 C. overnight and was then filtered and the solid washed with acetone precooled to 0 C. The washed solid consisted of a concentrate of the oleic acid together with the saturated acids, and on acidulation and vacuum distillation gave a colorless acid of I.V. 32.5. The filtrate and washings contained a concentrate of the linoleic acid, and on acidulation and vacuum distillation gave a pale yellow acid of I.V. 133.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. A process for separating a mixture containing mono-olefinic and poly-olefinic fatty acid compounds which comprises the steps of:

(a) forming acid-soaps of the mono-olefinic fatty acid compounds of said mixture in situ in which said acid soaps are selected from the class consisting of the sodium, potassium, and ammonium hydrogen di-alkenoates;

(b) maintaining said mixture at a temperature within the range from about 55 C. to about 25 C. in the presence of a low molecular weight organic solvent in which said acid-soaps of mono-olefinic fatty acid compounds are insoluble, whereby said acid-soaps of the mono-olefinic fatty acids precipitate as a solid phase; and

(c) separating said solid phase from the liquid phase.

2. The process of claim 1 wherein said mixture is a fraction of tall oil fatty acids.

3. The process of claim 1 wherein said mixture is a fraction of vegetable oil fatty acids.

4. The process of claim 1 wherein said mixture is a fraction of cottonseed oil fatty acids.

5. The process of claim 1 wherein said mixture is a fraction of the soyabean oil fatty acids.

6. The process of claim 1 wherein said mixture is a fraction of animal oil fatty acids.

7. The process of claim 1 wherein said mixture is oleine.

8. The process of claim 1 wherein said solvent is methanol.

9. The process of claim 1 wherein said organic solvent is acetone.

10. A process for separating a mixture containing mono-olefinic and poly-olefinic fatty acid compounds which comprises the steps of:

(a) forming acid-soaps of the mono-olefinic fatty acid compounds of said mixture in situ; said acid-soaps being selected from the class consisting of the sodium, potassium, and ammonium hydrogen fatty acids in which the fatty acids contain from 16 to 22 carbon atoms and have a mono-olefinic linkage;

(b) maintaining said mixture at a temperature within the range from about 55 C. to about 25 C. in the presence of an organic solvent in amounts sufficient to cause said acid-soaps of the mono-olefinic fatty acids precipitate as a solid phase, said organic solvent being selected from the class consisting of the alcohols and ketones containing not more than four carbon atoms; and

(c) separating said solid phase from the liquid phase.

11. The process for separating a mixture of fatty acids obtained from tall oil acids containing oleic acid compounds and having less than 2% by weight of resin acids which comprises the steps of:

(a) forming the sodium hydrogen dioleate of said mixture in situ;

(b) maintaining said mixture at a temperature from about -45 C. to about C. in the presence of from about two to ten parts by weight of methanol for each part by weight of said fatty acid mixture, whereby said sodium hydrogen dioleate is precipitated as a solid phase and (c) separating said solid phase from the liquid phase.

12. A process for separating a mixture of fatty acids obtained from tall oil containing oleic acid compounds and having less than two percent by weight of resin acids which comprises the steps of:

(a) forming the ammonium hydrogen dioleate of said mixture in situ;

(b) maintaining said mixture at a temperature within the range from about 30 C. to about 55 C. in the presence of from about two to ten parts of methanol for each part by weight of said fatty acid mixture, whereby the ammonium hydrogen dioleate precipitates as a solid phase; and

(c) separating said solid phase from the liquid phase.

13. The process for separating a mixture of fatty acids obtained from tall oil containing oleic acid compounds and having less than 2% weight of resin acids, which comprises the steps of:

(a) forming the sodium hydrogen dioleate of said mixture in situ;

(b) maintaining said mixture at a temperature within a range from about 45 C. to about 0 C. in the presence of about two to ten parts of acetone whereby said sodium hydrogen dioleate precipitates as a solid phase; and

(c) separating said solid phase from the liquid phase.

14. A process for separating the mixture of fatty acids obtained from tall oil containing oleic acid compounds and having less than 2% by weight of resin acids, which comprises the steps of:

(a) forming the ammonium hydrogen dioleate of said mixture in situ;

(b) maintaining said mixture at a temperature within the range from about 55 C. to about 10 C. in the presence of from about two to ten parts by weight of acetone for each part by weight of said fatty acid mixture whereby the ammonium hydrogen dioleate precipitates as a solid phase; and

(c) separating the solid phase from the liquid phase.

15. The process for obtaining a concentrate of linoleic acid from a mixture of cottonseed fatty acid compounds which comprises the steps of:

(a) forming the acid-soaps of the mono-olefinic fatty acid compounds of said mixture in situ in which said acid-soaps are selected from the class consisting of sodium, potassium, and ammonium hydrogen di-alkenoates;

(b) maintaining said mixture at a temperature from about 55 C. to about 25 C. in the presence of a low molecular weight organic solvent whereby said acid-soaps of the mono-olefinic acids precipitate as a solid phase;

(c) separating said solid phase from the liquid phase.

16. The process for obtaining a concentrate of linoleic acid from a mixture of soyabean fatty acid compounds which comprises the steps of:

(a) forming the acid-soaps of the mono-olefinic fatty acid compounds of said mixture in situ in which said acid-soaps are selected from the class consisting of sodium, potassium, and ammonium hydrogen di-alkenoates;

(b) maintaining said mixture at a temperature from about 55 C. to about 25 C. in the presence of a low molecular weight organic solvent whereby said acidsoaps of the mono-olefinic acid precipitate as a solid phase;

(c) separating said solid phase from the liquid phase.

Ralston: Fatty Acids and Their Derivatives, pub lished by Wiley and Sons (New York), 1948, pp. 287 and 288 relied on and pp. 888-890. 

1. A PROCESS FOR SEPARATING A MIXTURE CONTAINING MONO-OLEFINIC AND POLY-OLEFINIC FATTY ACID COMPOUNDS WHICH COMPRISES THE STEPS OF: (A) FORMING ACID-SOAPS OF THE MONO-OLEFINIC FATTY ACID COMPOUNDS OF SAID MIXTURE IN SITU IN WHICH SAID ACID SOAPS ARE SELECTED FROM THE CLASS CONSISTING OF THE SODIUM, POTASSIUM, AND AMMONIUM HYDROGEN DI-ALKENOATES; (B) MAINTAINING SAID MIXTURE AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT -55*C. TO ABOUT 25*C. IN THE PRESENCE OF A LOW MOLECULAR WEIGHT ORGANIC SOLVENT IN WHICH SAID ACID-SOAPS OF MONO-OLEFINIC FATTY ACID COMPOUNDS ARE INSOLUBLE, WHEREBY SAID ACID-SOAPS OF THE MONO-OLEFINIC FATTY ACIDS PRECIPITATE AS A SOLID PHASE; AND (C) SEPARATING SAID SOLID PHASE FROM THE LIQUID PHASE. 